Previous work has shown that feedback of information designed to induce self-awareness about contradiction existing within one's value-attitude system led to significant long-term changes in values, attitudes, and behavior that persisted as long as 21 months after a single experimental treatment. The main long-term theoretical objective of the proposed research will be to (a) extend earlier work on behavioral modification via value change to apply also to behavioral prevention, (b) to experimentally investigate several types of psychological inconsistency that might lead to the arousal of a process of value and behavioral change among those exhibiting health-destructive values and behavior, and to the arousal of a process of maintaining behavioral stability among those exhibiting health-constructive values and behavior, and (c) to experimentally investigate the separate and combined effects of frequency of arousal of inconsistency, social support, and social control on the long-term persistence of health-constructive values and behavior. The main applied objective will be to develop videotapes that can be widely employed in high school contexts to effectively influence adolescent smokers to quit or to reduce smoking on the one hand, and to deter non-smoking adolescents from starting to smoke on the other.